In the following description and claims rotatable outlet nozzles and rotors which at times are referred to as reaction swivels will be referred to collectively as "rotatable outlet nozzles".
Rotary sprinklers having a rotatable outlet nozzle have long been known. Such sprinklers typically fall into different categories depending among others on the means for rotating the outlet nozzle.
One category of such sprinklers comprise a housing with a water inlet and a water outlet nozzle adapted for rotating by a driving mechanism receiving its energy from the water inflow and successively transferring that energy to the rotatable outlet nozzle.
Such rotating driving mechanisms are known, for example, in U.S. Pat. No. 2,052,673 to Stanton, disclosing a rotary sprinkler motor in which a drive ball is displaced within a ball race into impacting engagement with an impeller element of the outlet nozzle, resulting in successive impacts, and a substantial continuous rotation of the nozzle. As a result there is emitted an essentially sharply defined water stream having a relatively large range.
Another type of such sprinklers, falling into a second category, typically comprise a rotor rotatably mounted with respect to an inlet portion formed with a through-flow tube. The rotor is provided with a deflecting surface adjusted to be impinged by a jet flowing axially from an outlet of said tube whereby, the jet is deflected laterally and the rotor is rotated. Such a sprinkler disclosed, for example, in U.S. Pat. No. 5,007,586 to Cohen.
It yet another type of rotary sprinklers, falling within a third category, are the hammer sprinklers in which both the rotary motion and the stream disruption are achieved by a hammer-impact mechanism.
It is known that the precipitation distribution of the water spray in rotary sprinklers is not homogenous along the radius of the spray and therefore does not fulfil irrigation requirements and attempts have been made to achieve substantially uniform irrigation within a given zone.
By the term "water precipitation" is meant the volume of water dispersed over a unit area during a unit of time. The water precipitation distribution is directly dependant on the square of a distance (R) from the sprinkler. Thus, in order to obtain an ideally uniform water distribution over a given area, means must be provided for compensating the regions nearer to the sprinkler.
The problem of non-homogenous water precipitation distribution becomes more severe when several sprinklers act jointly whereby overlapping zones of adjacent sprinklers (which naturally are remote from the sprinklers), will have an excessive water precipitation destination, where the zones near the sprinklers will have an inadequate distribution.
Various means have been proposed so to obtain an improved water precipitation distribution. For example, it is known to introduce discontinuities into the cross-section of the water outlet and in this way to disrupt the water spray. One known method to achieve this was to insert an adjusting screw into the nozzle near its discharge outlet and adjusting as desired the rate of penetration of the screw into the water stream.
Another method which has been suggested for obtaining an improved water precipitation distribution is by providing additional outlet apertures which are of very small size as compared with that of the main outlet aperture and are located substantially on the same side of the nozzle as the main outlet aperture. These additional apertures are intended to provide short range water coverage. It has been found however that the small outlet apertures frequently clog.
With hammer-impact sprinklers, the disruption of the stream is achieved by the hammer-impact as well as by an additional aperture and optionally an adjusting screw. A disadvantage of such impact hammer-type sprinklers resides in the fact that they are of a relatively complicated construction and are, on the one hand, relatively expensive and, on the other hand, faulty operation of the sprinkler is likely to require periodic maintenance and servicing.
It will furthermore be realized that the problem of non-uniform precipitation distribution cannot be solved by arranging merely for an increased precipitation in the region of the sprinkler (say up to 2 meters therefrom) seeing that this will usually be at the expense of precipitation at greater ranges.